In order to improve design quality and security feature of a magnetic card, providing a transparent optical diffraction layer for hologram image formation on the card is proposed and performed.
Formally, as the magnetic card with a hologram of high design quality in which a hologram image is especially formed on a magnetic recording layer, the card shown in FIG. 4 is proposed.
As for the magnetic card illustrated in this FIG. 4, an adhesive layer 51, a magnetic recording layer 52, an anchor layer 53, a metal deposited layer 54, a transparent optical diffraction layer 55, and a protective layer 56 are formed on a base material of a card 20.
Subsequently, metal, such as aluminum, is used for this metal deposited layer 54, and a hologram is formed by a light reflection at a boundary surface of a metal deposition layer and transparent optical diffraction layer; simultaneously, it plays a role which conceals hue of a magnetic recording layer, effectively.
On the other hand, as a method to improve design quality by enabling to recognize a background such as the magnetic recording layer visually rather than to conceal, a technology about a magnetic card with a transparent hologram is known (as refer to patent document 1).
In this patent document 1, instead of a metal deposited layer, a transparent layer which has a different refractive index from a transparent optical diffraction layer, adjoining a transparent optical diffraction layer was used to form transparent hologram, and a print layer formed on the magnetic recording layer is to be seen through the transparent hologram.
Then, in order to conceal hue of the magnetic recording layer and to improve design quality further, it is described that a concealing layer containing aluminum powder, etc., which has high ability for concealing the hue of the background layer, can be used between the magnetic recording layer and the print layer.
Also, as a technology about a magnetic card with a transparent hologram, the technology of making a print layer with higher design quality is known, in which high-luminosity reflecting ink layer is formed on a part of a region of one surface of the transparent hologram which has a transparent optical diffraction layer, (for example, as refer to patent document 2).
Further on the other hand, about a technology of forming an ink layer having the metal tone surface in a laminate, a lamination sheet for molding which has an ink layer containing metal flake and binder resin, with the content of metal flake of 3-60 mass % in the layer, and with coating thickness of 0.05-2 μm, being coated by micro gravure is reported (for example, as refer to patent document 3).
However, in the patent document 1, the concealing layer which conceals the hue of the magnetic recording layer is provided by being only paid attention to hiding hue of the magnetic recording layer, and any particular consideration is not taken about the reflectivity.
Usually, aluminum powder used for a concealing layer is the aluminum powder ground and stretched by a ball mill etc., and the reflectivity is low.
Therefore, since the concealing layer provided by using such aluminum powder had low reflectance and reflected light from the concealing layer was not able to be gained sufficiently, and there was a problem that a design of a hologram could not be visible finely and clearly.
Also, in the patent documents 2, although a high-luminosity reflecting ink layer with high reflectivity was formed; since the high-luminosity reflecting ink layer was formed only a part of a region of the surface of the transparent reflecting layer adjoined the transparent optical diffraction layer, reflected light from a region of a high-luminosity reflecting ink layer being not formed was not enough, and there was a problem that a hologram could not be visible finely and clearly.
The patent documents 1 and the patent documents 2 suggests to substitute a formation of high gloss coating having metal powder for the formerly-known metal deposited layer 54 as shown in FIG. 4.
However, in a magnetic card which was a configuration as shown in FIG. 4, since the highly conductive metal deposited layer 54 was used, there was a problem that an ESD (Electro Static Discharge) failure occurred.
Here, the ESD failure is: a phenomenon, which causes malfunction and destruction of the card reader when a magnetic card which has the metal deposited layer 54 on a magnetic recording layer 52 was used. In the ESD failure, electric charge accumulated in human bodies caused from static electricity, or electric charge accumulated in the magnetic card and/or the magnetic stripe caused from charging by contacting or rubbing of magnetic card and/or the magnetic stripe itself with the other objects, flows into the head of the card reader through the metal deposited layer 54 at the time of reading information recorded on this magnetic recording layer 52, and caused to malfunction and destruction of the card reader.
The ESD failure may occur not only in a magnetic card which has a metal deposited layer but also in a magnetic card which has a reflective layer or a concealing layer containing metal powder.
However, in the patent documents 1 and the patent documents 2, since the concealing layer or the reflecting ink layer was used only for the purpose of improving the external appearance of the magnetic card, and any consideration about the ESD failure was not paid; thus, there was a problem that a possibility of occurring the ESD failure was very high.
In a laminated sheet of the patent documents 3, an ink layer which has the luminous design of a metal tone including metal flake and binder resin is formed.
Then, formation of an ink layer with high reflectivity by micro-gravure coating is performed.
However, when these ink layer is applied as a reflective ink layer of card-like magnetic recording medium having a hologram, an investigation of composition and manufacturing method of the ink layer in detail is required in order to maintain high reflectivity of ink layer surface, and suppress the occurrence of the above-mentioned ESD failure, simultaneously.
However, such an investigation aiming at control of an ESD failure is not carried out so far.
Patent document 1: JP-A-2000-272275
Patent document 2: JP-A-2003-326824
Patent document 3: JP-A-2003-251754